It's the halfway point in the race across Canada. As the teams take to the ice flows of Hudson Bay, they cross from the province of Manitoba to the territory of Nunavut, an area the size of western Europe, inhabited by the Inuit. The ice is a hunting ground for seals and the polar bears who like to feed on them, It is also a favourite summer holiday spot for beluga whales.The next leg will take them from the edge of the Arctic to the shore of the Great Lakes – the fifth checkpoint over 3,000 kilometres away on Manitoulin Island. Situated in Lake Huron, it is the largest freshwater island on the planet, vast enough to contain over a hundred inland lakes itself.The race is on, but the pairs only have one way out of Churchill – a noisy overnight train south. Then, it's another sleepless night in two buses from hell as they join the road network towards the checkpoint. This single, gruelling stretch of highway – taking them into Ontario and skirting the Great Lakes – has limited transport options, and the teams will need ingenuity as well as stamina to gain the advantage in what could be the tightest leg so far.Much to Claudia's annoyance, Kevin splashed out on an expensive taxi in the last leg, so now the current leaders have just a quarter of their budget remaining. They decide that they must prioritise earning cash, or risk leaving the race. But can father and daughter negotiate the relentless travel network without falling out once more?Zainib is feeling homesick, so she and husband Mobeen must decide whether to take a gamble to take a break from the race so that Zainib can indulge her love of animals. However, she'll need to camp out for the first time to do so, and the pressure of hauling themselves back into contention takes its toll.Once off the Churchill train, Monique and Ladi try to make a quick break from the other teams, Although Ladi is impressed by his daughter continuing to take the lead, he is finding it hard to take a step back. And after receiving some bad news from home, Tricia fears she may have to cut her race short.It's the final push to reach that all important checkpoint to be one step closer to the finish line and the £20,000 cash prize.